J/ApJ/717/1067 Triggered star formation in SFO 38 (Choudhury+, 2010)
Triggered star formation and young stellar population in bright-rimmed
cloud SFO 38.
Choudhury R., Mookerjea B., Bhatt H.C.
<Astrophys. J., 717, 1067-1083 (2010)>
=2010ApJ...717.1067C 2010ApJ...717.1067C
ADC_Keywords: Photometry, infrared ; Photometry, UBVRI ; YSOs ; H II regions
Stars, pre-main sequence ; Spectral types
Keywords: H II regions - ISM: clouds - stars: pre-main sequence -
ISM: individual objects (SFO 38, IC 1396) - stars: low-mass
Abstract:
We have investigated the young stellar population in and around SFO
38, one of the massive globules located in the northern part of the
Galactic HII region IC 1396, using the Spitzer IRAC and MIPS
observations (3.6-24um), and followed up with ground-based optical
photometric and spectroscopic observations. Based on the IRAC and MIPS
colors and Hα emission, we identify ∼45 young stellar objects
(Classes 0/I/II) and 13 probable pre-main-sequence candidates. We
derive the spectral types (mostly K- and M-type stars), effective
temperatures, and individual extinction of the relatively bright and
optically visible Class II objects. Using the width of the Hα
emission line measured at 10% peak intensity, we derive the mass
accretion rates of individual objects to be between 10-10 and
10-8M☉/yr.
Description:
We have extracted IRAC (3.6, 4.5, 5.8, and 8um) and MIPS (24 and 70um)
observations from the Spitzer Space Observatory archive (Program ID
30050: Star Formation in Bright Rimmed Clouds by Fazio et al.
2006sptz.prop30050F).
SFO 38 was observed on 2009 July 17, August 23, and September 15 using
Bessell's broadband filters VR, BVI, and BI, respectively, and on 2008
November 4 using the narrowband Hα (900s) with the Himalayan
Faint Object Spectrograph Camera (HFOSC) mounted on the 2m Himalayan
Chandra Telescope (HCT) of the Indian Astronomical Observatory, Hanle.
Medium resolution (∼7Å) spectra were obtained for relatively bright
and optically visible YSOs during July-November of both 2008 and 2009
in the wavelength range (5200-9200Å) with the HFOSC mounted on the
HCT. Typical exposure time of each spectrum was 3600s.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 159 110 *Results of near- and mid-IR photometry of the
mid-infrared sources in SFO 38
table3.dat 60 44 BVRI photometry of MIR sources in SFO 38
table4.dat 85 29 Spectral classification of YSOs
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Note on table1.dat: Out of the 110 sources identified with Spitzer in SFO 38,
80 were found to have NIR counterparts (in 2MASS, Cat. II/246). However 10 out
of the 80 sources with NIR counterparts were found to coincide with the H2
knots identified by Beltran et al. (2009, Cat. J/A+A/504/97).
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See also:
II/311 : WISE All-Sky Data Release (Cutri+ 2012)
II/246 : 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)
J/MNRAS/415/103 : IPHAS T Tauri candidates in IC 1396 (Barentsen+, 2011)
J/A+A/504/97 : JHKs photometry of IC 1396N (Beltran+, 2009)
J/MNRAS/396/964 : T Tauri in and around bright-rimmed clouds (Chauhan+, 2009)
J/AJ/135/2323 : Hα stars and HH objects near BRCs (Ikeda+, 2008)
J/ApJ/654/316 : X-ray sources in IC 1396N (Getman+, 2007)
J/AJ/123/2597 : Hα stars and HH objects near BRCs (Ogura+, 2002)
J/A+A/309/581 : CO observations of clouds in IC 1396 region (Weikard +,1996)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 7 A7 --- Name SFO 38 source name (<[CMB2010] MIR-NNN> in
Simbad)
8 A1 --- r_Name [ab] JHKs photometry reference if not 2MASS (1)
10- 11 I2 h RAh Hour of right ascension (J2000)
13- 14 I2 min RAm Minute of right ascension (J2000)
16- 20 F5.2 s RAs Second of right ascension (J2000)
22 A1 --- DE- Sign of declination (J2000)
23- 24 I2 deg DEd Degree of declination (J2000)
26- 27 I2 arcmin DEm Arcminute of declination (J2000)
29- 33 F5.2 arcsec DEs Arcsecond of declination (J2000)
35- 39 F5.2 mag Jmag ? 2MASS J-band magnitude
41- 44 F4.2 mag e_Jmag ? Jmag uncertainty
46 A1 --- l_Hmag Limit flag on Hmag
47- 51 F5.2 mag Hmag ? 2MASS H-band magnitude
53- 56 F4.2 mag e_Hmag ? Hmag uncertainty
58- 62 F5.2 mag Ksmag ? 2MASS Ks-band magnitude
64- 67 F4.2 mag e_Ksmag ? Ksmag uncertainty
69- 73 F5.2 mJy F3.6 ? Spitzer/IRAC 3.6um flux density
75- 78 F4.2 mJy e_F3.6 ? F3.6 uncertainty
80- 85 F6.2 mJy F4.5 ? Spitzer/IRAC 4.5um flux density
87- 90 F4.2 mJy e_F4.5 ? F4.5 uncertainty
92- 97 F6.2 mJy F5.8 ? Spitzer/IRAC 5.8um flux density
99-102 F4.2 mJy e_F5.8 ? F5.8 uncertainty
104-109 F6.2 mJy F8.0 ? Spitzer/IRAC 8.0um flux density
111-114 F4.2 mJy e_F8.0 ? F8.0 uncertainty
116-122 F7.2 mJy F24 ? Spitzer/MIPS 24um flux density
124-127 F4.2 mJy e_F24 ? F24 uncertainty
129-134 A6 --- Class Preliminary classification (Trans., III/S, I,
II, I/II, 0/I, Galaxy, H2) (2)
136-158 A23 --- Comm Comments
159 A1 --- f_Comm [c] c: variable in J/H/Ks
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Note (1): JHKs photometry reference as follows:
a = Nisini et al. 2001A&A...376..553N 2001A&A...376..553N
b = Beltran et al. 2009, Cat. J/A+A/504/97
Note (2): Preliminary classification based on selected color-color plots and
other criteria described in Section 3.2.
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 8 A8 --- Name SFO 38 source name (MIR-NNN mainly)
10- 14 F5.2 mag Bmag ? HCT/HFOSC B-band magnitude
16- 20 F5.3 mag e_Bmag ? Bmag uncertainty
22- 26 F5.2 mag Vmag HCT/HFOSC V-band magnitude
28- 32 F5.3 mag e_Vmag Vmag uncertainty
34- 38 F5.2 mag Rmag HCT/HFOSC R-band magnitude
40- 44 F5.3 mag e_Rmag Rmag uncertainty
46- 50 F5.2 mag Imag HCT/HFOSC I-band magnitude
52- 56 F5.3 mag e_Imag Imag uncertainty
58- 60 A3 --- Var [BVI ] Variability (1)
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Note (1): We consider a source to be variable if the magnitude difference is
≥0.1mag at the two observing epochs (2009 Aug 23 and Sept 15).
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 8 A8 --- Name SFO 38 source name (MIR-NNN mainly)
10- 17 A8 --- AName Alternate name (BRC38= <[OSP2002] BRC 38 NN>
or GFG= <[GFG2007] NN> in Simbad)
19- 26 A8 "DD/MM/YY" Date Observation date
28- 35 F8.3 0.1nm W Hα equivalent width (Å)
37- 38 A2 --- SpT MK spectral type
40 I1 --- e_SpT ? Subtype uncertainty
42- 45 I4 K Teff ? Effective temperature
47- 50 A4 --- Type YSO type (CTTS/WTTS: Classical or Weak TTau)
52- 57 F6.2 km/s Ha ? Hα emission line at 10% of the peak
intensity (Hα[10%]) (1)
59- 64 F6.2 [Msun/yr] logdM/dt ? Rate of accretion from Hα emission (1)
66- 70 F5.2 --- alpha ? IRAC slope
72- 75 F4.2 mag E(V-I) ? V-I color index
77- 80 F4.2 mag Av ? Extinction (2)
82- 85 F4.2 mag Erat ? E(V-I)/E(B-V) color index ratio
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Note (1): Natta et al. (2004A&A...424..603N 2004A&A...424..603N) showed that Hα[10%]≥200km/s
can be used to distinguish the accretors and nonaccretors as well as
to derive an approximate estimate of the accretion rate dM/dtac
quantitatively by the following relation:
logdM/dtac=-12.89(±0.3)+9.7(±0.7)x10-3Hα[10%] where
Hα[10%] is in km/s and dM/dtac is in M☉/yr.
Note (2): Using the V-I color of a particular spectral type and our optical BVRI
observations, we calculated the AV assuming the normal interstellar
extinction law as given by Bessell & Brett (1988PASP..100.1134B 1988PASP..100.1134B). The
average extinction toward the globule is estimated to be AV=2.5mag.
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History:
From electronic version of the journal
(End) Emmanuelle Perret [CDS] 05-Jun-2012